1. Field of the Invention
The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device with improved color quality and a method of fabricating the same.
2. Discussion of the Related Art
For an image display device which displays a variety of information on a screen as a core technology in advanced information and communication, there is continuous progress in development of thin, light-weight, and portable devices with improved performance. Hereupon, an organic light emitting display device for controlling light intensity of an organic light emitting layer is recently receiving attention as a flat panel display device, along with demand for a flexible display capable of being bent pursuant to convenience and space utilization.
The organic light emitting display device includes a thin film transistor (TFT) array part formed on a substrate, an organic light emitting display panel disposed on the TFT array part, and an encapsulation layer to isolate the organic light emitting display panel from the external environment. The organic light emitting display device applies an electric field to a first electrode and a second electrode formed at both ends of an organic light emitting layer so as to inject and transport electrons and holes into the organic light emitting layer, thereby utilizing an electroluminescence phenomenon which emits light by binding energy during recombination of the electrons and holes. The electrons and holes, which are paired with each other in the organic light emitting layer, emit light while falling from an excited state to a ground state.
In detail, in the organic light emitting display device, a plurality of sub-pixels is defined by intersections of gate lines and data lines. Each of the sub-pixels receives a data signal from the data line when a gate pulse is supplied to the gate line, resulting in generating light corresponding to the data signal.
Hereinafter, a conventional organic light emitting display device will be described with reference to FIG. 1.
FIG. 1 is a cross-sectional view illustrating a conventional organic light emitting display device.
As shown in FIG. 1, the conventional organic light emitting display device includes a substrate 10, a TFT formed on the substrate 10, a protective film 16 formed to cover the TFT, a color filter layer 17 formed on the protective film 16, an overcoat layer 18 formed to cover the color filter layer 17, and an organic light emitting cell 20 formed over the overcoat layer 18. The organic light emitting cell 20 includes a first electrode 20a, an organic light emitting layer 20b, and a second electrode 20c sequentially stacked.
The TFT includes a gate electrode 11a, a gate insulating layer 12, a semiconductor layer 13, a source electrode 15a, and a drain electrode 15b. If the semiconductor layer 13 is an oxide semiconductor layer, the TFT further includes an etch stop layer (ESL) 14 formed on the semiconductor layer 13.
The first electrode 20a is electrically connected to a drain electrode 15b through a drain contact hole (not shown) formed by selectively removing the protective film 16 and the overcoat layer 18. A bank 19 having a bank hole that exposes a portion of the first electrode 20a to define a luminescent region is formed on the overcoat layer 18. Then, the organic light emitting layer 20b is formed in the bank hole, and the second electrode 20c is formed over the entire surface of the organic light emitting layer 20b. 
Such an organic light emitting cell 20 emits light by binding energy generated while holes from the first electrode 20a and electrons from the second electrode 20c are injected into the organic light emitting layer 20b and combined with each other. In addition, an encapsulation layer may further be formed on the second electrode 20c for capping the organic light emitting cell 20.
The encapsulation layer is attached to the organic light emitting cell 20 via a face seal 22 disposed on one surface of a glass cap 30. Particularly, in order to prevent inflow of moisture and oxygen into the organic light emitting layer 20b, an inorganic layer 21 may further be disposed between the face seal 22 and the second electrode 20c. 
The organic light emitting display device may realize various colors of light using white light emitted from the organic light emitting layer 20b while the white light from the organic light emitting layer 20b passes through the color filter layer 17 formed in each of the sub-pixels. However, since light emitted from the organic light emitting layer 20b sequentially passes through the overcoat layer 18, the color filter layer 17, the protective film 16, the gate insulating layer 12, and the substrate 10 and is emitted to the outside, color inversion is caused by wavelength interference of light according to viewing angle while passing through the protective film 16 and the gate insulating layer 12 having high indexes of refraction, thereby changing color coordinates according to the viewing angle.